Pyruvic acid and pyruvates (pyruvic acid esters) are important intermediates for perfumes, food additives, and electronic materials as well as raw materials for various bioactive substances such as antiviral drugs. It is used as flavours for food.
Conventionally pyruvic acid is produced by dehydrative decarboxylation of tartaric acid. Silica-supported pyrosulfate catalyst (K2S2O7/SiO2) is used for synthesis of ethyl pyruvate in continuous mode with up to 60% yields at the high temperature of 300° C. This reaction requires excess KHSO4 as a dehydrating agent, leading to an expensive and wasteful process. Pyruvate can also be obtained by a microbial process, using strains of yeast and E. coli. However, both strains require precise regulation of media composition during fermentation and complex supplements.
Article titled “New technique on synthesis of ethyl pyruvate” by Chen Sufang et al. reports ethyl pyruvate was synthesized from ethyl lactate using TBHP as oxidant and TBAB as phase transfer catalyst, the purity of product was over 98%. The reaction is environment friendly and easy to operate, it provides a new method to synthesize ethyl pyruvate from ethyl lactate.
U.S. Pat. No. 5,053,527 discloses a process for the manufacture of alkyl pyruvates having the general formula: CH3—CO—COOR; wherein R represents a C1-C8 alkyl radical, by oxidation of the corresponding alkyl lactate, the improvement comprising; admixing a 30 to 70% by weight aqueous hydrogen peroxide solution into a solution of the alkyl lactate in an organic water-immiscible solvent containing a catalytic quantity of bromine while maintaining a temperature of 15°−30° C.
Article titled “Titania-catalysed oxidative dehydrogenation of ethyl lactate: effective yet selective free-radical oxidation” by Enrique V. Ramos-Fernandez et al. published in Green Chemistry, 2014, 16, pp 3358 reports the catalytic oxidative dehydrogenation of ethyl lactate, as an alternative route to ethyl pyruvate. Testing various solid catalysts (Fe2O3, TiO2, V2O5/MgO—Al2O3, ZrO2, CeO2 and ZnO). The liquid phase oxidation of ethyl lactate 1 was carried out in a 400 ml stirred autoclave (Biometa, fitted with a system for liquid sampling) at 403 K and at constant pressure of 1 MPa of pure oxygen. The catalyst (2 g) was immersed in 200 g of ethyl lactate. In experiments using a solvent, mass ratio of 1:1 (solvent:reactant) was used.
Article titled “Catalytic activity of iron phosphate doped with a small amount of molybdenum in the oxidative dehydrogenation of lactic acid to pyruvic acid” by Mamoru Ai published in Applied Catalysis A General 234(1):235-243 reports both the catalytic activity and the selectivity of iron phosphate in the oxidative dehydrogenation of lactic acid to form pyruvic acid increase dramatically by doping a very small amount of molybdenum compounds. Both the highest activity and selectivity are obtained at a Mo/Fe atomic ratio ranging from 0.01 to 0.3. The catalytic activity and selectivity are not affected if the source of Mo6+ is changed. Effects similar to those for the Mo6+ doping are not observed in the cases of the doping of V5+ or W6+. The functions of Mo6+ were studied.
Article titled “Efficient oxidative dehydrogenation of lactate to pyruvate using a gas-liquid micro flow system” by Toshiya Yasukawa et al. published in Industrial and Engineering Chemistry Research, 2011, 50 (7), pp 3858-3863 reports an efficient production of pyruvate by the oxidative dehydrogenation of lactate is achieved using a micro flow system based on gas-liquid slug flow. In this micro flow system, oxidizing agents and acetonitrile solutions of lactates and vanadium species are used, and lactate is converted into the corresponding pyruvate. For reasons of atom economy and enhanced mass transfer of oxygen into the liquid phase, due to internal circulation flow within slugs, molecular oxygen is the preferred agent. In a catalyst screening, vanadium oxytrichloride (VOCl3) gave the highest pyruvate yield. A continuous system is developed, consisting of the following two processes using T-shaped mixers: the mixing of an acetonitrile solution of lactate with that of VOCl3 and the injection of oxygen gas into the solution mixture. Compared with the conventional batch system, the oxidative dehydrogenation of lactate to the corresponding pyruvate proceeds more effectively using this micro flow system.
Chinese Pat. No. 1060759 discloses the catalytic oxidation synthesis of pyruvate is characterized by that in the presence of modified silver or copper catalyst said invention uses gas phase atmospheric oxidation of lactate to prepare pyruvate. Its dressing agent is a halide, and one or several kinds of P, Zr, Zn and K also can be added. Its reaction temp. is 300-600 deg. C., and according to different technological processes, the crude pyruvate products with low concentration and high concentration can be respectively prepared, and after rectification the invented refined product can be obtained. There are a variety of methods known in the art for preparing pyruvic acid esters, for example ethyl lactate, petroleum ether, sodium dihydrogen phosphate, potassium permanganate reacted together, with potassium permanganate as the oxidizing agent lactate, and acetone esters evaporated. Also some hydrogen peroxide as an oxidant lactate production and pyruvate. Such methods are adding an oxidizing agent in the lactate ester in the liquid phase oxidation of lactate to pyruvate, and then isolated and purified.
U.S. Pat. No. 4,229,590 reports alkyl pyruvates are prepared by oxidizing alkyl lactates in the presence of a silver catalyst of a defined particle size, at from 450° to 700° C. The products are starting materials for the preparation of drugs, synthetic resins and plastics.
US Pat. No. 887,795 reports a method for preparing a pyruvate ester is disclosed. In the method of the present invention, a lactate ester is oxidized by hydrogen peroxide in the presence of a Ti—Si molecular sieve catalyst. In the present invention, the Ti—Si molecular sieve catalyst is easily filtered and recycled, the reaction conditions are mild due to the usage of hydrogen peroxide, the process is simple and easily performed, the conversion rate of the lactate ester is high, and the selectivity of the pyruvate ester is high.
Chinese Pat. No. 104276951 discloses an aqueous-phase catalytic oxidation method for preparing lactate pyruvate, Pt load which bismuth compound or Pd as catalyst and molecular oxygen as oxidant, water as solvent, the selective and efficient preparation of pyruvate oxidation lactates, The process mild reaction conditions, high selectivity, the catalyst can be reused, has important application prospects.
Chinese Pat. No. 1359893 discloses a process for preparing ethyl pyruvate is characterized by that the reaction of the mixture of ethyl lactate vapour and air at 250-300 deg. C. in the presence of silica gel carried silver catalyst. Its advantages are high conversion (80%) and selectivity (90%), and high activity and selectivity of catalyst. Therefore, there is a need to develop a suitable catalyst for high yield synthesis of ethyl pyruvate from ethyl lactate.